Topical drug delivery to the eye has always been an attractive route of administration, but there has been limited success in finding effective carriers that can effectively overcome the physical and physiological barriers for a drug to reach the anterior and posterior segments of the eye. In their earlier patent application, PCT/GB2008/004233, the inventors described the problems encountered when using eye drops which are the usual route of topical drug administration to the eye. Further, the inventors provided a carrier for use in topical drug administration which enables the delivery of drugs to the rear segments of the eye, without the need for direct invasive administration.
There has been a further demand for non-invasive delivery systems, with the advent of treatments targeting VEGF (vascular endothelial growth factor) in blinding conditions such as AMD (age-related macular degeneration) and DR (diabetic retinopathy), which currently use intraocular (intravitreal) injections as the route of administration. With increasing rates of ageing diseases and diabetes, the need for therapies is rising steeply, especially those that are not invasive, easy to administer and inexpensive. Improved carriers for topical delivery of pharmaceuticals to inhibit VEGF, and treat AMD, DR and other similar conditions would be useful.
Development of therapeutics for the central nervous system (CNS) and the eye is one of the most challenging areas in drug development, especially with systemic administration. This is primarily because of the blood-retinal barrier (BRB) in the eye and the blood-brain barrier (BBB) in the CNS. Despite recent advances, the BBB remains a real problem in preventing many potential therapeutic agents reaching the CNS. The current challenge is to develop drug-delivery systems that ensure that drugs cross the BBB in a safe and effective manner.
Drugs which have until now been used in CNS treatments have been limited by having to be small, relatively lipid-soluble compounds which pass across the BBB by means of transmembrane diffusion. In addition, as in Alzheimer's disease, passive and active immunization have been used—but again the main difficulty being that antibodies cross the BBB poorly, with IgG molecules in particular having poor penetration due to their large size.
The inventors have developed carriers that enable agents to cross the BBB and BRB. Such carriers may be used in pharmaceuticals for administration in a variety of methods, such as intravenous, nasal, transdermal and topical administration.